This invention relates to the handling of a plurality of sheets of conveyed sheet material, such as corrugated paperboard and the like. The concept of the invention provides an improvement over devices such as that disclosed in copending U.S. patent application Ser. No. 906,059 filed May 15, 1978, entitled "Shingling And Stacking Of Conveyed Sheet Material", by Carl R. Marschke and assigned to a common assignee.
In such devices, a plurality of sheets are passed through a shingling station and then conveyed to a sheet stacker. A nip is disposed at the entrance to the stacker and through which the shingled sheets pass. The nip comprises a pair of nip rollers with the lower roller positioned so that the trailing end portion of each sheet drops off the lower roller onto the stack being formed.
It has been discovered that, at least in some instances, as a sheet drops off the lower nip roller it tends to shift or skew sideways, sometimes by a substantial amount. This is undesirable in that the stack formed as the sheets engage the backstop will not be uniform in horizontal dimension.
It is an aim of the present invention to handle the shingled sheets in such a manner that undesirable shifting or skewing of the sheets is substantially reduced or prevented.
In accordance with the invention, an anti-skew device is positioned between the stacker input nip and the stacker itself. In the embodiment disclosed, the device comprises a plurality of fingers mounted along a transverse mounting element disposed between the nip and the stacker. The fingers are designed to normally hang downwardly, but some of them are raised upwardly as they are engaged by a sheet passing therebeneath, and rest on top of the moving shingled sheets. The transverse mounting element is longer than the width of the sheets and some of the fingers disposed outwardly of the sheets continue to hang down and provide an alignment guide to hold the longitudinal sheet edges against shifting or skewing. The downwardly hanging outer fingers are disposed adjacent the side edges of the formed stack to hold the upper sheets therein in alignment.